This invention relates to heat-recoverable articles, especially heat-shrinkable articles.
Heat-recoverable articles are well known and, in their most common form comprise a heat-shrinkable sleeve which is made from a polymeric material capable of having the property of plastic or elastic memory imparted to it. This sleeve is expanded at an elevated temperature to a diameter greater than its normal diameter and is then cooled while being maintained in the enlarged dimension. A sleeve treated in this manner will retain its expanded dimensions until it is again heated, at which time it will recover towards its original shape. Examples of heat-recoverable sleeves may be found in U.S. Pat. Nos. 2,027,962 (Curries) and 3,086,242 (Cook et al), the disclosures of which are incorporated herein by reference.
Such sleeves find many applications especially in the connection and termination of wires, cables and pipes. However, there are many instances where it is desirable to provide a sealing, insulating or protective closure member for elongated objects, for example, cables and pipes, where the ends of the elongated objects are not accessible, or if accessible, where it is undesirable to disconnect or otherwise displace them from their original position. For such applications so-called "wrap-around sleeves" have been developed. Basically, these are heat-recoverable sheets of material which can be wrapped around the substrate to form a generally tubular shape and which are generally provided with means for holding them in the wrapped-up configuration during recovery, although in some cases this may be achieved on site, for example by the use of suitable adhesives. Various types of heat-recoverable wrap-around sleeves are described, for example, in U.S. Pat. No. 3,379,218 and British Pat. Nos. 1,155,470, 1,211,988 and 1,346,479 the disclosures of all of said patents being incorporated herein by reference.
Such heat-recoverable wrap-around sleeves have proved extremely successful in many applications. However, one further problem which has been encountered in the insulation and sealing of extended elongated substrates has been the effective sealing of members which branch out from the main substrate; one particular instance of this is where a power cable branch joins a main power cable. In such situations the use of a simple wrap-around sleeve is not possible and, whilst attempts have been made with varying degrees of success to use such heat-recoverable wrap-around sleeves in conjunction with other means such as mastic coatings, no satisfactory simple solution has to date been found. The problem is especially acute with pressurised cable.
It is an object of this invention to provide a novel heat-recoverable article which can be manufactured in a simple manner yet which can successfully be used in the installation and repair of break-out joints from main line cables and overcome the problems set forth above.